Signals at different radio frequency bands, or “multiband signals” or “multi-band signals,” are frequently used in various wireless communication applications, such as portable wireless communication devices. Examples of multiband RF communication technologies include but not limited to CDMA bands BC0/1/16, GSM bands 2/3/5/8, WCDMA bands 1/2/4/5/6/8, TD-SCDMA bands 34/39, FDD LTE bands 1/2/3/4/5/7/8/12/13/17/20/25/26, TDD LTE bands 38/39/40/41, GPS, Wi-Fi bands at 2.4 GHz and 5 GHz, and others.
Various commonly used multiband multi-radio system designs are based on a combination of multiple single-band bandpass filters, duplexers, and switches for handling multiband radio operations, such as out-of-band noise and interference, spurious emission, and antenna isolation. Such single-band bandpass filters and duplexers are discrete components and are typically used to separately filter their corresponding RF signals at different RF carrier frequencies when a given filter or duplexer is selected by a switch. For example, to feed the RF signals into a multiband antenna, a single-pole multiple-throw (or “SPxT”) switch is typically employed to multiplex the RF signals into a signal feeding port of the multiband antenna. However, using a SPxT switch would not allow the device to simultaneously operate under multiple RF communication protocols.